Voltage regulators are used for providing voltage sources for operating analog circuitries. These voltage sources may include supply voltages (e.g., VDD) and reference voltages (e.g., VREF). A load circuit that receives the voltage source may experience a change of impedance during operations, such that the corresponding load current may be operation dependent. For instance, a digital-to-analog conversion (DAC) circuit typically includes a resistor network that has a variable resistance depending on a digital code. The DAC circuit operates to convert the digital code to an analog signal by manipulating the resistor network under a reference voltage. When the variable resistance changes according to the digital code, the resistor network may drain a different amount of load current to a ground source. In the likely scenario where the ground source includes parasitic elements, the changing load current will cause the ground voltage to fluctuate. The fluctuating ground voltage directly impacts the stability of the reference voltage. As a result, the performance and reliability of the DAC circuit may become code-dependent.
To alleviate the code-dependency of the DAC circuit, attempts have been made in the past to use a ground buffer in conjunction with a voltage regulator. The ground buffer operates to stabilize the ground voltage of the resistor network by means of a feedback control mechanism. However, the ground buffer generally increases the design complexity, the power consumption, and the size of the overall circuit. The deployment of ground buffers thus becomes infeasible in systems with stringent design constraints. Accordingly, there is a need for a voltage regulator that can provide a relatively stable voltage source without incurring the design costs of a ground buffer.